The present invention relates to the molding and stripping of golf ball cores from compression mold plates and in particular to an apparatus having three mold plates to produce golf ball cores with dual parting lines.
Rubber balls are frequently molded by compression. In compression molding there are usually two mold plates, bottom and top, each of which has a plurality of insert cavities of hemispherical dimension. The composition to be molded is distributed in cylindrical slugs to the bottom mold cavities. Usually the bottom mold plates have cavities that are truncated spheres of greater than hemispherical dimension, while the cavities of the top mold plate are truncated spheres of less than hemispherical dimension as seen in U.S. Pat. No. 4,389,365. The molds are generally aligned in rows as in a muffin tin with from 200 to 400 or more being a typical number of molds per press. The cavities of the bottom mold generally have cross-sections at their top section, which are smaller in dimension than the greatest cross-section of the ball. When the mold plates are parted, the balls will all remain in the cavities in the bottom mold plate, where they are subsequently removed by a pop-up pin design coupled with a stripping fixture plate which is manually operated. A consistent problem is that the pins in their normal operation do generate a high force, which often distorts some of the ball cores in their South Pole area. The mold plates are brought together under heat and pressure as a result of which the rubber expands and fills the spherical cavities of the opposed mold plates. Since it is undesirable to have any voids in the balls, there is usually employed a slight excess of material which exits out of the mold during the ball formation into an overflow area. This excess material cures into scrap or xe2x80x9cflash.xe2x80x9d The scrap is typically ground up and reincorporated into future core material without degrading the properties of the cores, and disposing of scrap adds costs to the making of cores. Another factor influences scrap formation during core molding. Typically, the half-molds are fixed within mold frames so that they cannot move during molding. Differential thermal effects and mechanical mismatches of the half-molds can cause dimensional errors within the molds. As a result, the half-molds can be misaligned during molding. This allows excess pre-form material to escape the cavity. This excess material contributes to the undesirable formation of scrap. These errors can also cause the cores to be out of round. Out-of-round cores can form unplayable golf balls. When the mold plates are parted, the balls all remain in the cavities in the bottom mold plate, where they are subsequently removed along with the flashing by action of the pop-up pins that are located in a base of which the bottom mold plate rests upon.
A manually operated stripping plate is generally used to separate the ball cores from the flashing. This is a very labor intensive procedure which assumes that the ball cores will be held by the flashing long enough to have the stripper plate pass underneath to separate ball core from flashing.
The instant invention presents a method and apparatus to address the above problems, particularly as to providing a means for reducing product defects and reducing the amount of excess flash or scrap.
The present invention is directed towards an improved method for stripping a plurality of golf ball cores from a mold plate and the flashing that engulfs the cores. The instant invention utilizes a three-plate mold with improved positive retention of the cores in the center of the three plates, thereby allowing for efficient handling by an automated or semi-automated ball core removal system. The improvement in handling the ball cores will reduce product defects.
The present invention provides for an improved method of forming ball cores that consists of three mold plates. The top mold plate contains cavity inserts that consist of core geometry above the core equator. The center mold plate contains cavity inserts having geometry below the core equator and is placed in an intermediate position relative to the core equator and the South Pole of the core. Finally, the inserts of the bottom mold plate contain the remaining core geometry to complete the sphere.
The method of removing the cores comprises first, lifting the top plate immediately upon the mold exiting the press, thereby exposing the center plate containing the molded ball cores. Then lifting while simultaneously rotating the center plate to an angle beyond 90xc2x0 where it is juxtaposed against a stripping fixture plate with the South Pole area of the cores exposed. And finally, pushing out the remaining cores with a low force from behind the center plate wherein the cores are passed through openings of the fixture plate. The flashing remains in the molding fixture for further handling. The plate handling procedure is automated.
The present invention also provides for the production of golf ball cores having dual parting lines. A first parting line being spaced from a first pole (North Pole) by a first distance, and a second parting line being spaced from an opposite second pole (South pole) which of the core by a second distance less than the first distance.